https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78063
Bug ID: 78063
Summary: libbacktrace fails to handle cross CU
DW_AT_abstract_origin
Product: gcc
Version: 7.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: other
Assignee: unassigned at gcc dot gnu.org
Reporter: rguenth at gcc dot gnu.org
CC: iant at google dot com
Target Milestone: ---
Currently libbacktrace doesn't handle the pending early LTO debug way of
separating early debug and late debug. We have
Compilation Unit @ offset 0xfcc:
Length: 0x111 (32-bit)
Version: 4
Abbrev Offset: 0x362
Pointer Size: 8
<0><fd7>: Abbrev Number: 1 (DW_TAG_compile_unit)
<fd8> DW_AT_producer : (indirect string, offset: 0x1574): GNU C11
7.0.0
20161020 (experimental) -mtune=generic -march=x86-64 -g -O2 -O2
-fsanitize=addr
ess -flto -fno-use-linker-plugin -flto-partition=none
<fdc> DW_AT_language : 12 (ANSI C99)
<fdd> DW_AT_name : (indirect string, offset: 0x1523):
/space/rguent
her/src/svn/trunk/gcc/testsuite/c-c++-common/asan/misalign-1.c
...
<1><10cb>: Abbrev Number: 14 (DW_TAG_subprogram)
<10cc> DW_AT_external : 1
<10cc> DW_AT_name : foo
<10d0> DW_AT_decl_file : 1
<10d1> DW_AT_decl_line : 9
<10d2> DW_AT_prototyped : 1
<10d2> DW_AT_type : <0xff6>
and
Compilation Unit @ offset 0xe37:
Length: 0x191 (32-bit)
Version: 4
Abbrev Offset: 0x296
Pointer Size: 8
<0><e42>: Abbrev Number: 1 (DW_TAG_compile_unit)
<e43> DW_AT_producer : (indirect string, offset: 0x13c4): GNU GIMPLE
7.
0.0 20161020 (experimental) -mtune=generic -march=x86-64 -mtune=generic
-march=x
86-64 -g -O2 -O2 -O2 -O2 -fmath-errno -fsigned-zeros -ftrapping-math -fno-trapv
-fno-strict-overflow -fno-openmp -fno-openacc -fsanitize=address
-fno-use-linker
-plugin -flto-partition=none
<e47> DW_AT_language : 12 (ANSI C99)
<e48> DW_AT_name : (indirect string, offset: 0x14de): <artificial>
<e4c> DW_AT_comp_dir : (indirect string, offset: 0x14eb):
/abuild/rguen
ther/obj/gcc
<e50> DW_AT_ranges : 0x40
<e54> DW_AT_low_pc : 0x0
<e5c> DW_AT_stmt_list : 0x290
<1><e60>: Abbrev Number: 2 (DW_TAG_imported_unit)
<e61> DW_AT_import : <0xfd7> [Abbrev Number: 1]
...
<1><e65>: Abbrev Number: 3 (DW_TAG_subprogram)
<e66> DW_AT_abstract_origin: <0x10cb>
<e6a> DW_AT_low_pc : 0x400ac0
<e72> DW_AT_high_pc : 0x59
<e7a> DW_AT_frame_base : 1 byte block: 9c (DW_OP_call_frame_cfa)
<e7c> DW_AT_GNU_all_call_sites: 1
<e7c> DW_AT_sibling : <0xe9d>
so we run into
static int
read_function_entry (struct backtrace_state *state, struct dwarf_data *ddata,
struct unit *u, uint64_t base, struct dwarf_buf *unit_buf,
const struct line_header *lhdr,
backtrace_error_callback error_callback, void *data,
struct function_vector *vec_function,
struct function_vector *vec_inlined)
{
...
case DW_AT_abstract_origin:
case DW_AT_specification:
if (abbrev->attrs[i].form == DW_FORM_ref_addr
|| abbrev->attrs[i].form == DW_FORM_ref_sig8)
{
/* This refers to an abstract origin defined in
some other compilation unit. We can handle
this case if we must, but it's harder. */
break;
}
if (val.encoding == ATTR_VAL_UINT
|| val.encoding == ATTR_VAL_REF_UNIT)
{
const char *name;
name = read_referenced_name (ddata, u, val.u.uint,
error_callback, data);
if (name != NULL)
function->name = name;
}
which causes us to fail to specify the function name to the dwarf_lookup_pc
callback. This causes libsanitizer to not print file/line info but fall
back to symbolic backtrace completely (it could at least preserve the
partial info I guess). Which in turn causes most asan and tsan tests
in the testsuite to FAIL with -flto because they scan for a proper
backtrace but we get
READ of size 4 at 0x7fff24ce1c8f thread T0
#0 0x400b18 in foo (/home/abuild/rguenther/obj/gcc/misalign-1.exe+0x400b18)
#1 0x40092c in main
(/home/abuild/rguenther/obj/gcc/misalign-1.exe+0x40092c)
instead of the desired
READ of size 4 at 0x7fff2193ea1f thread T0
#0 0x400b98 in foo
/space/rguenther/src/svn/trunk2/gcc/testsuite/c-c++-common/asan/misalign-1.c:11
#1 0x4009af in main
/space/rguenther/src/svn/trunk2/gcc/testsuite/c-c++-common/asan/misalign-1.c:35
as said, libbacktrace computes file and line correctly but fails to lookup
the function DW_AT_name as that is only available in the abstract origin.
